Tourism to Catalonia has slumped by 15% in the two weeks since the region’s controversial referendum on independence, according to industry experts.

August’s terror attacks in Barcelona and the seaside resort of Cambrils, which left 16 people dead, scarcely dented tourist numbers, but images of police violence and huge rallies around the 1 October vote on independence are taking their toll.

There has been no sign of tensions easing between the Catalan and Spanish governments following the vote, which has led to Spain’s biggest political crisis for 40 years, and has seen thousands turn out on the streets for opposing protests for and against the independence movement.

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José Luis Zoreda, vice-president of the tourist association Exceltur, said tourist activity in Catalonia had fallen by 15% in the weeks following the referendum compared to the same period last year.

Catalonia welcomed about 18 million visitors last year, and tourism accounts for about 12% of the region’s GDP, with industry and trade as the other main contributors. More than 400,000 people in Catalonia depend on the tourist industry for employment.

Zoreda added that bookings were “in freefall of around 20% for the last quarter of 2017, especially in Barcelona, in what is normally the high season for conferences, leisure and shopping tourism”, especially among international tourists.

A 20% decline would represent a loss of around €1.1bn, according to Zoreda. Exceltur says this decline is confined to Catalonia and there is no slump in the rest of Spain.

In its statement on Thursday, the Spanish government reiterated its claims that the recent push for Catalan independence was damaging the economy, criticising the regional authorities for “deliberately and systematically seeking institutional confrontation, despite the serious damage it’s causing to coexistence and Catalonia’s economy”.

“In a short period of time our hotels have seen rooms cancelled because conferences have been put on hold,” said Alfonso del Poyo, vice-president of Meliá Hoteles Internacional. Meliá has eight hotels in Catalonia, five in Barcelona, and saw reservations fall by 4% after 1 October.

“The situation is very worrying, especially for those who depend on the international market,” Del Poyo said.

Tourists pose for selfies in front of the Sagrada Familia basilica in Barcelona in August Photograph: Lluis Gene/AFP/Getty Images

A Barcelona restaurant owner who owns several establishments but who wished to remain anonymous said they had seen a considerable downturn.

“Over the past two weeks bookings have been down 30-40% and people have been cancelling right through to January,” the restaurant owner said. “We employ 350 people and here in Barcelona what we’re facing is an economic tsunami. But when I tell people this they say if I don’t like it I should move to Madrid.”

Barceló Hotels and Resorts, which has three hotels in Barcelona, also noted a drop in reservations but a spokesman for the group said it was “not alarming”.

Barcelona is the cruise capital of the Mediterranean but this month two ships chose to dock in Valencia instead. The city is also one of Europe’s top destinations for conferences but the political situation has led at least one major conference, the European Association of Chambers of Commerce and Industry, to cancel.

“We’ve certainly seen a slowdown in bookings, as well as somecancellations, during what is normally one of the busiest times of the year,” said James Blick, co-founder of Devour Tours, which offers food and wine tours throughout Spain.

“Tourists are highly sensitive to any whiff of instability … news headlines, images and videos of police and voter clashes on 1 October were clearly enough to scare a significant number of people away. Happily though, as tourists, we generally have short memories and once stability returns, so does tourism.”

The downturn does not appear to have affected areas outside the region’s main cities. Jordi Urpi, who runs a small hotel in rural Tarragona, says he hasn’t noticed any change. “We’re full up to till the end of October, as always. Fewer bookings during the week, but that’s normal at this time of year, both for local and international clients.”

The online holiday lettings platform Airbnb did not offer any figures but its rival HomeAway said it had not had a significant number of cancellations.

• The photograph on this article was changed on 20 October 2017. An earlier image showed a picture of firefighters supporting protestors, but was captioned as being of police restraining Catalans.